JPH0250147B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to hot melt adhesives. More specifically, the present invention relates to a hot melt adhesive that has excellent adhesion to various substrates, particularly water-resistant adhesion, and extremely good storage stability. Conventionally, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, etc.
Products containing ethyl acrylate copolymers as their main components have been widely used in industrial fields such as automobiles, aircraft, building materials, and communications. However, these adhesives do not have sufficient adhesion, especially in terms of water-resistant adhesion, so their adhesive strength decreases dramatically when immersed in water or exposed to moisture. Its use has been limited in fields where durable adhesiveness is required. On the other hand, as a method to improve the adhesion of ethylene polymers, the method of introducing polar groups into them is also widely used, but in this case, the adhesion between the adherend and the adhesive polymer is caused by hydrogen bonding. Therefore, the bonding strength is easily broken due to the intrusion of moisture, and the water-resistant adhesion is still insufficient. Adhesives made of ethylene copolymers containing epoxy groups, such as ethylene-vinyl acetate-glycidyl methacrylate ternary copolymers, are also known, and when bonded at a sufficiently high temperature, significant improvements can be made. However, in many fields of application, adhesion at such high temperatures cannot be adopted due to constraints on the softening temperature and deterioration of the adherend. Furthermore, as a method of improving adhesion to substrates such as glass and metal, methods such as mixing or graft copolymerizing an organosilane compound with an ethylene polymer such as polyethylene or ethylene-vinyl acetate copolymer are also known. However, in this case, there is a problem that the adhesive strength decreases over time while the adhesive is left to stand until it is used, or that the adhesive strength is insufficient under the relatively low temperature and short time adhesive conditions required in practice. There are drawbacks such as inability to obtain adhesive strength. In view of these current circumstances, the present inventors have developed a method that can stably obtain high adhesive strength even when bonded under relatively low temperature and short-time conditions, has sufficient water-resistant adhesion, and has storage stability. As a result of various studies in search of a hot-melt adhesive that is excellent for hot melt adhesives, we found a silane-grafted modified version of an olefin copolymer having a glycidyl group, or a mixture of this and a silane-grafted modified version of an olefin copolymer that does not have a glycidyl group. It has been found that the above-mentioned problems can be effectively solved by using the following methods. The present invention therefore relates to such hot melt adhesives. The olefin copolymer having a glycidyl group to be modified by silane grafting is ethylene-vinyl acetate-glycidyl (meth)acrylate ternary copolymer or ethylene-(meth)acrylic acid lower alkyl ester-glycidyl (meth)acrylate 3 The original copolymer is used, preferably ethylene-vinyl acetate-glycidyl methacrylate 3
The original copolymer is used. In addition, as olefin polymers that do not have glycidyl groups and are also modified by silane grafting,
Ethylene-vinyl ester copolymers represented by polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-butadiene copolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid Examples include ethylene-unsaturated carboxylic acid lower alkyl ester copolymers such as ethyl copolymer, ethylene-butyl acrylate copolymer, and ethylene-methyl methacrylate copolymer, preferably ethylene-vinyl acetate copolymer. is used. The melting point of these olefin-based (co)polymers is
Preferably it is about 60-100°C. If the melting point is too high, the adhesion will be poor when bonded under low temperature and short time conditions.On the other hand, if the melting point is too low, the adhesive strength will not only be low in high temperature atmospheres, but also
This becomes a problem when used in film or sheet form. Specifically, for example, in the case of an ethylene-vinyl acetate-glycidyl methacrylate ternary copolymer, the sum of the contents of vinyl acetate and glycidyl methacrylate in the copolymer is about 10 to 30% by weight, in which glycidyl methacrylate The content of is about 0.5
-20% by weight, and in the case of ethylene-vinyl acetate copolymers, the vinyl acetate content is about 10-30% by weight. Examples of unsaturated alkoxysilane compounds for silane graft modification of these olefinic (co)polymers include vinylsilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, and vinyltriacetoxysilane. , acryloxypropyltrimethoxysilane, methacryloxypropyltrimethoxysilane, and other acrylic silanes, and acrylic silanes are particularly desirable for obtaining better water-resistant adhesion and storage stability. . Silane graft modification is carried out by adding an olefinic (co)polymer as a base polymer, an unsaturated alkoxysilane compound, and a radical polymerization initiator to a temperature above the melting point of the base polymer and a radical polymerization initiator using an extruder, kneader, Banbury mixer, etc. This is carried out by melt-kneading at a temperature higher than the decomposition temperature of the polymerization initiator or by reacting in a solution. The amount of grafting is generally about 0.2 to 4% by weight based on the base polymer. If the amount of grafting is more than this, the fluidity of the graft modified product will be reduced, and the adhesiveness will be reduced, and the storage stability will also be deteriorated, which is economically disadvantageous. On the other hand, if the amount of grafting is less than this, the effect of improving adhesiveness, particularly water-resistant adhesiveness, cannot be sufficiently obtained. Hot melt adhesives have these olefin (co)polymer silane graft modified products as essential components, and these essential components can be used in the following embodiments. (1) Single silane graft modified product of an olefin copolymer having a glycidyl group (2) A mixture of the above silane graft modified product and a silane graft modified product of an olefin copolymer not having a glycidyl group (3) Glycidyl group A silane graft modified product of a mixture of an olefinic copolymer having a glycidyl group and an olefinic polymer not having a glycidyl group. The mixing ratio of the silane graft modified copolymer depends on the content of glycidyl groups, but it is generally preferable to be about 20% by weight or more, and if the mixing ratio is less than this, sufficient water-resistant adhesion will not be achieved. It is difficult to obtain stability and storage stability. (4) To these silane graft-modified products or mixtures thereof, add the above-mentioned base polymer to be modified with silane grafts, that is, an olefinic copolymer having a glycidyl group, within a range that does not impair the desired adhesiveness, especially water-resistant adhesiveness. A mixture of unmodified polymers or olefinic polymers that do not have glycidyl groups Hot melt adhesives containing these as essential ingredients may contain tackifiers, waxes, plasticizers, process oils, fillers, etc. as necessary. Agents, stabilizers, etc. are appropriately mixed and used. The hot melt adhesive according to the present invention has adhesive properties,
The reason why the water-resistant adhesion and storage stability are especially excellent is not necessarily clear, but the following may be considered. In other words, alkoxysilane groups are hydrolyzed by moisture on the surface of substrates such as glass, ceramics, and metals during heat bonding, become silanol groups, and react with the substrate surface to form covalent bonds. It is known that a large bonding force is generated at the interface between the substrates and the adhesion is improved.
When adhesion is performed at a relatively low temperature and for a short period of time, it is difficult to obtain practically sufficient adhesion, especially water-resistant adhesion, and storage stability is also not necessarily sufficient. On the other hand, olefinic copolymers with epoxy groups derived from glycidyl groups react with the surface of the substrate when bonded at high temperatures, resulting in high adhesive strength, but they fail to bond at relatively low temperatures and for short periods of time. If this is the case, a strong bond will not form with the surface of the substrate, and contact with hot water or moisture will easily reduce its adhesion. However, in the case of the graft modified product used in the hot melt adhesive according to the present invention, since an epoxy group is present in addition to an alkoxysilane group, sufficient adhesion, especially water-resistant adhesion, cannot be achieved when using it. Therefore, it can be suitably applied to substrates such as glass and ceramics, and further improvement in storage stability can be observed. Next, the effects of the present invention will be explained with reference to Examples. Example 1 Ethylene-vinyl acetate-glycidyl methacrylate terpolymer (vinyl acetate content 6% by weight,
Glycidyl methacrylate content 4% by weight, melt index 6) 100 parts (weight, same below),
2 parts of γ-methacryloxypropyltrimethoxysilane and 0.4 part of 1,1-bis(tert-butylperoxy)3,3,5-trimethylcyclohexane as a radical initiator were added, and the mixture was
A graft modified product was produced by melt-kneading using a 30 mm diameter extruder at a resin temperature of 180°C. The produced graft modified product was heated at 150℃ and 100Kg/
cm ² G for 5 minutes using a heated press to form a sheet with a thickness of 1 mm, from which an adhesive test piece was prepared as follows and the 180° peel strength was measured. The adhesive test piece was formed by sequentially stacking a graft modified sheet and a Teflon sheet on a flat glass, and pressing the sheets together with a hot press at 140° C. for 3 minutes to form a flat glass/graft modified sheet laminate. This adhesive test piece was immersed in warm water at 60° C. for 5 days, and the peel strength before and after immersion was measured as normal adhesive strength and water-resistant adhesive strength, respectively. In addition, the graft modified sheet was heated at 60°C and relative humidity at 50°C.
% for 25 days under high temperature and high humidity conditions, an adhesive test piece was prepared in the same manner using this, and its water resistant adhesive strength was evaluated as storage stability. Example 2 In Example 1, 50% of another ethylene-vinyl acetate-glycidyl methacrylate ternary copolymer (vinyl acetate content 5% by weight, glycidyl methacrylate content 4% by weight, melt index 6)
and 50 parts of ethylene-vinyl acetate copolymer (vinyl acetate content 19% by weight, melt index 15) was used as the base polymer to be grafted, and the produced graft modified sheet ( However, the same evaluation was conducted for a hot press temperature of 160°C. Example 3 In Example 2, silane graft modification was performed using 100 parts of ethylene-vinyl acetate copolymer,
A mixture of equal amounts of the obtained graft modified product and the graft modified product obtained in Example 1 was kneaded at a resin temperature of 140°C using a 30 mm diameter extruder to obtain a graft of a copolymer having no glycidyl group. A mixture of the modified product and a graft modified product of a copolymer having a glycidyl group was obtained. The produced graft modified mixture was molded into a sheet and evaluated in the same manner as in Example 2. Example 4 In Example 2, the same amount of ethylene-ethyl acrylate copolymer (ethyl acrylate content: 17% by weight,
Melt index 25) was used and the graft modification was carried out on equal mixtures thereof. Regarding the produced graft modified product mixture, the same sheet and sheet evaluation as in Example 2 were also performed. Example 5 Ethylene-n-butyl acrylate-glycidyl methacrylate terpolymer (n-butyl acrylate content 7.2% by weight, glycidyl methacrylate content 10.2% by weight, melt index 6)
To 100 parts, 2 parts of γ-methacryloxypropyltrimethoxysilane and 0.4 parts of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane as a radical initiator were added, and the mixture was heated to a diameter of 30 mm. The mixture was melt-kneaded using an extruder at a resin temperature of 230° C. and a screw rotation speed of 40 rpm to produce a graft modified product. Example 1 Regarding the produced graft modified product
The same sheet molding and sheet evaluation were performed. Example 6 Ethylene-isobutyl methacrylate-glycidyl methacrylate terpolymer (isobutyl methacrylate content 26% by weight, glycidyl acrylate content 1.4% by weight, melt index 15) 100
2 parts of γ-methacryloxypropyltrimethoxysilane and 2,5 parts as a radical initiator.
- Add 0.4 parts of dimethyl-2,5-bis(tert-butylperoxy)hexane and mix the mixture with 30 mm
A graft modified product was produced by melt-kneading using a diameter extruder at a resin temperature of 230°C and a screw rotation speed of 40 rpm. Example 1 Regarding the produced graft modified product
The same sheet molding and sheet evaluation were performed. Comparative Example 1 Regarding the base polymer ethylene-vinyl acetate-glycidyl methacrylate terpolymer used in Example 1, the same sheet molding and sheet evaluation as in Example 1 were performed. Comparative Example 2 Regarding the graft modified product of the ethylene-vinyl acetate copolymer obtained in Example 3, the same sheet molding and sheet evaluation as in Example 1 were performed. The results obtained in each of the above Examples and Comparative Examples are shown in the following table. 【table】

Claims (1)

[Claims] 1. Ethylene-vinyl acetate-glycidyl (meth)
A hot melt adhesive comprising an unsaturated alkoxysilane compound graft modification of an acrylate terpolymer or an ethylene-(meth)acrylic acid lower alkyl ester-glycidyl (meth)acrylate terpolymer. 2 Ethylene-vinyl acetate-glycidyl (meth)
Unsaturated alkoxysilane compound graft modified product of acrylate terpolymer or ethylene-(meth)acrylic acid lower alkyl ester-glycidyl (meth)acrylate terpolymer and unsaturated olefin polymer without glycidyl group A hot melt adhesive comprising a mixture of graft modified alkoxysilane compounds. 3. The hot melt adhesive according to claim 2, wherein an ethylene-vinyl ester copolymer is used as the olefin polymer having no glycidyl group. 4. The hot melt adhesive according to claim 2, wherein an ethylene-unsaturated carboxylic acid lower alkyl ester copolymer is used as the olefinic polymer having no glycidyl group.